Apply F4 DMA2 errata if LED_STRIP is using DMA2 #10880
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| @@ -88,6 +90,10 @@ void setUsedLedCount(unsigned ledCount); | |||
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| bool isWS2811LedStripReady(void); | |||
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| #ifdef STM32F4 | |||
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There is no need to make the contents of header files conditional - this is normally not done in Betaflight, unless it serves to avoid build problems.
| @@ -221,4 +221,12 @@ void ws2811LedStripDMAEnable(void) | |||
| TIM_Cmd(timer, ENABLE); | |||
| xDMA_Cmd(dmaRef, ENABLE); | |||
| } | |||
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| #ifdef STM32F4 | |||
| bool ws2811LedStripDMA2Errata(void) | |||
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'ws2811LedStripUsesDma2()` to make this a bit more indicative of what it returns?
| */ | ||
| const bool dshotBitbangActive = isDshotBitbangActive(&motorConfig()->dev); | ||
| const bool dshotBitbangActive = isDshotBitbangActive(&motorConfig()->dev) || ws2811LedStripDMA2Errata(); |
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dshotBitbangActive isn't correct any more - dma2HasErrataConflict or dma2isUsed?
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Sorry to have wasted your time on this @mikeller. I realise that, just like timer based DSHOT the LED_STRIP DMA uses a peripheral target of a timer's capture/compare register which is mapped on the APB1/2 bus, not the AHB bus. Therefore this errata does not apply in this case. Therefore abandoning this PR as not needed. The following configuration is possible on a MATEKF411. |
The errata at https://www.st.com/resource/en/errata_sheet/dm00037591-stm32f405407xx-and-stm32f415417xx-device-limitations-stmicroelectronics.pdf, section 2.1.10, reports an errata that corruption may occur on DMA2 if AHB peripherals (eg GPIO ports) are, accessed concurrently with APB peripherals (eg SPI busses).
Bitbang DSHOT uses DMA2 to write to GPIO ports and this has already been handled to not enable DMA on an SPI bus using DMA2. There are instances where the LED_STRIP driver may also use a timer associated with DMA2, and it is this case that this PR addresses.
The MATEKF411 target, for example, defines the
LED_STRIPresource thus:Referring to Table 9, Alternate function mapping, in the STM32F411CE data sheet it can be seen that pin A08 is associated only with TIM1.
From the BF CLI we can see that the only DMA streams associated with TIM1 are on DMA2.
This PR ensures that under such circumstances if LED_STRIP is disabled then DMA will be enabled for the gyro and marked as owned by
GYRO_CSthus:Whereas if LED_STRIP is enabled, we instead get the following indicating the gyro SPI access will be polled only.
The following explores the issue of DMA stream assignment on F4 processors a little more, and this will be significant when #10573 is merged which supports using DMA to retrieve gyro data over SPI and achieve much tighter gyro and PID cycle times.
There are compromises presented by the F4 processors with respect to DMA. Using the MATEKF411 as an example, with no motors or LED strip enabled the following DMA streams are assigned supporting DMA access for both OSD and gyro.
If the motors are enabled using DSHOT with the default settings it can be seen that the timer based DSHOT uses streams that would otherwise be available for the OSD.
If anything but the simplest of OSD displays are used this will impact flight performance.
If, however, DSHOT is enabled using bit-banged DMA the OSD DMA is available, but the gyro DMA is not.
Given that the gyro DMA is no longer available, one might think there's no harm is then enabling the LED_STRIP, however as the F411 does not have TIM8, TIM1 may be used by either bit banged DSHOT or LED_STRIP, but not both.
Therefore in order to enable LED_STRIP it is necessary to disable big-banged DSHOT resulting in the following.
DMA is no longer available for either the OSD or gyro.
LEDs are clearly less important than flight performance, and arguably so is the OSD, so one might consider disabling both of these and achieving the following DMA stream assignment.
Contrast this with the FURYF4OSD with by having more considered motor pin assignments is able to achieve the following. This supports four motors, OSD, FLASH and gyro SPI DMAs.
However enabling LED_STRIP results in a conflict as shown below whereby MOTOR 3 can't be mapped.
If one really must use LED_STRIP then enabling bit-banged DSHOT will result in the following assignment, forcing the gyro's SPI access to be polled.